How To Read A Sectional Chart

Looking intently over the instrument panel directly in front of us, my seven year old son and I went back and forth. “Is that it?” He called, pointing over one way. “No, I don’t think so,” I replied. “There! Those lights – is that it!?” He called back. “Those look like runway lights to me. Let’s start down and line up.” My son, Reid, and I were on the home flight simulator. As he has practiced and gained more ability, what used to be slamming the throttle to full power and yanking back on the stick to take off and do crazy maneuvers has morphed into a much more skilled demonstration of what he’s learned. The mission today was to take off from one airport and land at another. Pulling out our map and plotter, we chose the short hop between Gwinnett (KLZU) and Peachtree Dekalb (KPDK). Drawing a line between the two airports, we reviewed how to measure both the miles between them and the course direction. I asked him if he remembered the compass directions. Pointing to each cardinal direction clockwise from the top, he replied “Never – Eat – Soggy – Waffles.” Today’s flight headed waffles (west) so we took off and pointed that way with the compass. In addition to knowing which way to fly, we use “pilotage” to compare what we see outside to what is on our map. Today, let’s look around the map we used for our flight to learn some of the basics of the aviation map, called a sectional chart.

1. Airports

There is a lot of data packed into a little bit of space when you know what to look for.

Airports that have a control tower are shown as a blue symbol, like Gwinnett, where we took off. The magenta ones don’t have a control tower. Instead, they are pilot controlled, meaning pilots announce their position to other pilots on the radio instead of having a controller watch it all. Next to each airport symbol is an information block of text about the airport. Let’s read through the block for Gwinnett:

The airport identifier is LZU. We can contact the tower on 124.1. The star means that the tower operates part time, so the little blue “C” means that the tower frequency turns into the Common Traffic Advisory Frequency when the tower is closed. We get our weather, or Automatic Terminal Information Service (ATIS), on 132.275. On the last line, the airport elevation is 1062 feet. The *L means that the runways are lighted (the L), but with limitations (the asterisk). This asterisk usually means that the pilot can control the runway lights by keying the microphone button on the CTAF frequency. The 60 means that the longest runway is 6000 feet long (it is always shown in hundreds). Finally, 123.05 is the Unicom Frequency.

At the top of the airport symbol, the open star means that a rotating light beacon is turned on from sunset to sunrise. The ticks on the left, right and bottom indicate fuel is available.

2. Obstructions

The famous Plant Branch stack in Milledgeville is a 1007 foot stack. It will soon be torn down, but has provided a great visual landmark for many pilots.

The triangles with a dot in them (much like the A’s in the Clayviation logo) are obstruction symbols. These are usually towers and stacks. The smaller triangles are for obstructions over 200ft high. If they are over 1000ft high, they have the taller symbol. If they have little lightning bolts coming from the top, this doesn’t mean they shoot lightning (or do they?) – this just means that they have high intensity lights. Finally, look at the two numbers by the obstruction. The one in parenthesis is how tall the obstruction is. The number without parenthesis is the height of the top of the obstruction in relation to mean sea level. Basically, it’s what your altimeter would read.

3. Airspace Rings

Knowing what kind of airspace you are in is important for two main reasons: Who you need to be talking to and what sort of visibility and cloud clearance you need to have to fly. While airspace is a whole blog to itself, let’s just cover some basics. The airspace categories are A, B, C, D, E, and G. They generally move from more restrictive (A) to the least restrictive (G). For the purposes of today’s flight, let’s break down how to find each one:

–Class A is only above 18,000 feet so you won’t find it charted on the map.
–Class B is around the busiest airports like Atlanta and are shown with light blue bands. Looking near Gwinnett, you can see the blue band of Atlanta’s Class B pass just to the west of the airport.

This is Atlanta’s Class B Airspace as seen by the light blue band circling nearly the entire picture.

–Class C has a solid magenta band.

Chattanooga’s Class C Airspace is shown by a solid magenta band.

–Class D (like around Gwinnett) has a dashed blue band.

Gwinnett is surrounded by Class D airspace and marked by the dashed blue line. The thick magenta band is a “bowl” of airspace, lowering the class E from 1200ft down to 700ft.

–Class G airspace is usually from the ground 1200ft (mountainous areas out west have some special cases).
-You can think of Class E airspace as “filling in everywhere else.” You’ll notice lots of thick magenta rings with a hard edge that fades to a solid edge. There is one around around Gwinnett. This is a little bowl of airspace that dips that class E at 1200ft down to 700ft above the ground in that area. An area with a dashed magenta band means that the Class E is brought all the way down to the surface.

4. VOR’s

VOR’s can be easily found by the large compass ring that surrounds them. The VOR at Athens (KAHN) is right on the airfield.

As a navigation aid, Very High Frequency Omni Directional Radio Ranges are usually easier to navigate than they are to say. Just stick with calling it a “VOR.” From the station (a small building with a white cone on the top), radio signals are sent out in every direction, almost like spokes on a bike tire. A pilot can basically hop on any of the radials using an instrument in the airplane and follow the radial to or away from the station. You’ll find the VOR at the center of the large compass ring on the map. Each VOR has an information box that shows its frequency and identifier. Look for the box to say either VOR, VORTAC, or VOR DME (all variations on the VOR, but works the same to us). Once the frequency is tuned in the airplane, you can turn it up to listen to the Morse code. This is how you make sure you are receiving the right signal.

5. Airways

This airway is charted as a light blue line and follows the 092 radial from the Athens VOR.

Because of the popularity of navigating between VOR stations, the light blue lines are airways between two stations that show you the course direction already measured for you.

6. Terrain

The different terrain elevations and features are shown as varying shades of color ranging from greens (lower elevations) through tans up to browns (higher elevations). Contour lines show lines of equal elevation. You’ll notice the very large blue numbers (A five-nine in the picture above). This is the Maximum Elevation Figure. In each quadrangle (black box of latitude and longitude) of the map, this number is the highest elevation or obstruction in that sector. It is in hundreds of feet, so in this case, 5,900 feet is the highest thing in that region.

Around mountainous areas, it’s easy to see how the shading and contouring changes rapidly.

7. Roads & Railroads

Because they are such good visual aids from the air, major roads and railroads are shown along with the towns they connect.

The gray lines are the roads, while the black lines with the cross hatches are the railroads.

8. Water Features

Lakes, rivers and oceans are shown in blue. Out here where I live in “Georgia’s Lake Country,” they make for easy visual checkpoints.

Lakes are very prominent features to use as a visual aid to navigation.

9. City Lights

All of the yellow shown around more dense areas are basically what the city lights will look like from above at night. While primarily useful for night flight, it also gives an indication of denser buildings and population, which is useful for day flight as well.

If you flew near Milledgeville at night, it would look something like the yellow area from above.

10. Power Lines

You might be wondering how you could see or navigate tiny wires. Actually, it isn’t as much the wires as much as the path cut through the trees that is easy to spot from the air. Sure, you can see the various poles and structures that hold the wires, but the path cut through the woods makes them easy to spot.

Power lines are a great visual tool from the air, but pilots generally don’t like power lines up close.

Map Your Course

These items are certainly not everything that you will find on a map, but whether you are a student pilot or even a passenger on a flight, knowing some of these basics will help a complicated mess of data turn into meaningful information. While you can pick up a Sectional Chart at most airports, you can also order them online here. You can get them either one by one or with a chart subscription. With a subscription, one is mailed to you each time a new one is published (usually every 6 months). When I was in my initial training, my primary source of navigating was comparing my map to what I saw outside. Now my iPad shows the same map, but the GPS drops my position right on the screen. It kinda feels like cheating. But even with the convenience of technology I always fly with a paper backup. You just can’t beat the battery life and reliability of a paper chart.

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5 Comments

Thanks for the info Clay, I stumbled on you through a StuckMic email this morning. Glad to hear you nailed your sUAS cert! I’m in the process of studying myself, and resources like this are highly valuable to me! Sectionals are where I’m focusing most intently right now. I’m not a pilot yet but I share your passion for flight, and it started with FS 2004! I’ve been flying UAS for about a year and a half now and yes, that’s my new passion. It’s opened up a new world for me. I just retired this year and am having a blast, can’t wait to get my remote pilot cert to see where this will wind up. I’m stoked at the opportunities! My website listed below hasn’t gone live yet, but the template is a work in progress! There’s link’s to a couple of my older videos. I have the Autel X-Star Premium and absolutely love it, especially the camera! Please keep in touch!

Thanks for the listen, Kevin! I’m looking forward to seeing some of your footage! Indeed the world of drones is a really cool one. Seeing how much airspace knowledge is necessary to fly will likely open up some doors to more pilots being made from UAV pilots. Please let me know if I can help in any way in your journey!